Globally, demand for aromatics, such as benezene, toluene and xylene, is increasing by an annual average of 4 to 6%. That is, demand for aromatic products is rapidly increasing to such a degree that the increase rate of the demand for aromatics approximates two times of the increase rate of GDP and three times of the increase rate of demand for petroleum products. Particularly, such an increase of demand is caused by the increase of demand for aromatics in China.
Conventionally, aromatic products (benzene/toluene/xylene) have been produced by hydrotreating and extracting pyrolysis gasoline produced together with main basic oil fraction products such as ethylene, propylene and the like in a naphtha cracking center using naphtha as a raw material, or by the reformate from a catalytic naphtha reforming process and separating.
However, due to the rapid increase in demand for aromatics, the supply of naphtha in the world market, including in China, have become increasingly tight since 2007. Further, conventional technologies for producing aromatic products cannot keep up with the increase in aromatic demand because they use only naphtha, which is an oil fraction having only a narrow boiling range of crude oil. Therefore, the feedstock for aromatic products, which can replace naphtha, are required.
Meanwhile, fluidized catalytic cracking (FCC) is a typical process for producing gasoline from heavy oil. Recently, a lot of FCCs has greatly been constructed.
Typical products obtained by FCC may include propylene, MTBE, alkylate, LCN (light cracked naphtha), HCN (heavy cracked naphtha), LCO (light cycle oil), SLO (slurry oil), and the like. These products are respectively used as raw materials of synthetic resins, an oxygen-containing fraction for gasoline, a high-octane fraction for gasoline, a compounding agent for gasoline, a compounding agent for diesel oil/heavy oil, a compounding agent for heavy oil, and the like.
However, all over the world, quality standards for gasoline and diesel are becoming stricter. As the regulation of the content of aromatics in diesel becomes stricter, additional treatment of the above-mentioned FCC semi-processed products is required. However, among these FCC semi-processed products, LCO (light cycle oil) includes a large amount (70% or more) of aromatic components having one or more rings, so additional treatment of LCO requires high hydrogen consumption, thereby greatly increasing utility cost.
Further, LCO is not suitable as a raw material in a conventional aromatic production process using naphtha because heavy aromatics of two or more rings must be converted into one ring aromatics, and catalyst poisoning components such as sulfur and nitrogen must be removed, although it may be possible to use LCO for producing aromatic products instead of naphtha.
However, as mentioned above, considering the rapid increase of demand for aromatics and the failure in supply of naphtha, it is expected that pressing problems in oil refining and aromatic producing industries will be simultaneously solved by inducing the production of aromatics using an oil fraction including aromatic compounds such as LCO and the like produced in the FCC process.
U.S. Pat. No. 4,585,545 discloses a method of producing high-octane gasoline containing a large amount of aromatic components using LCO (light cycle oil) obtained from FCC. However, the gasoline from this method doesn't have a high value-added product because it includes a large amount of low-value aromatics Further, this method is ineffective one as a fuel reforming technology because the issue of environmental regulation has lately attracted more considerable attention compared to the issue of an increase in octane number of gasoline.
Further, U.S. Pat. No. 6,565,739 discloses a method of producing naphtha and light olefin using LCO obtained from FCC. However, naphtha produced by this method includes a very small amount of aromatic components, because aromatic components are completely saturated in an intermediate hydrogenation process. Therefore, this method is not suitable for solving the above-mentioned problems.